If you have ever looked at an oscilloscope waveform of the AC coming out of
your wall sockets at home, you know what the word ugly means. Our power
grids are wallowing in noise and grundge coming from everywhere. You not
only have to deal with the motor in your refrigerator, but the motor in your
neighbor's refrigerator as well.

All those miles and miles of AC
power lines make excellent antennae too, and there are plenty of radio
frequency sources sending RF our way.

An audio amplifier processes
all frequencies passing through it, not just the audible frequencies. RF -
let's call it 100 kHz and above - can "beat" with the audible band
frequencies, cause oscillations that we can't hear, but decrease the
amplifier's performance.

So, what can we do about it?

Over the past few decades, a
number of products have arisen for consumers use, to form a category we call
"Power Conditioners". Up until recently, they consisted of various arrays of
filters, including coils (inductors, chokes), graphite, and capacitors.
Usually, some sort of surge protection (fuses, MOVs) is thrown in.

Do they work?

Well, they do, sort of. Since
they are filters, and filters are not perfect, you end up with reduction
(attenuation) of the noise, but not complete elimination. However, second
and third harmonics of 60 Hz, that is, 120 Hz and 180 Hz, are so close to
the fundamental (60 Hz), their removal is all but impossible.

Finally, a solution . . . .

In the past couple of years, a
new breed of power conditioner has arisen. Rather than filter out the noise
and harmonics, they restore the original 60 Hz waveform. PS Audio's P300,
P600, and P1200 are legendary in this regard. In fact, we use the P1200
here. They are basically audio amplifiers that take the incoming AC, convert
it to DC in the power supply, and then output it as 60 Hz, 120 Volts AC
(your receiver amplifier outputs sound at all frequencies and about 30 volts
AC). They work beautifully, but are inefficient, since they are audio
amplifiers. So, if you want 1,200 watts output, you need about 2,000 watts
coming from the wall sockets.

The ExactPower approach . .
. .

The EP15 reconstructs the AC
waveform too, but uses a completely different procedure. Instead of
converting the AC to DC and back again to AC, the ExactPower looks at the AC
waveform, and having a picture of the ideal sine wave in its memory, it
removes peaks and also fills in the gaps, in a real time fashion. Also, the
EP15 is a voltage regulator, and since our big home theater systems can
require big time power during critical movie passages, this is an important
feature, because a lowered voltage can make that deep bass sound wimpy.

At $1,799, the EP15 is not
really very expensive for what it does, when you take into account previous
power conditioner designs that cost that much, but just filter out some of
the noise, and do not regulate the voltage.

It is a very attractive unit
too, with a green LED readout panel on the front that lets you see what the
voltage is, along with how many watts you are using. The rear panel sports a
large number of AC sockets. There are eight high grade sockets to be exact,
along with a grounded AC socket for detachable power cords. It is a 15 amp
unit, which means you don't need one of those weird AC wall receptacles that
would be required by code if it were a 20 amp unit.

The Tests

The first thing I did was put
the EP15 on an oscilloscope and look at the AC waveform. First of all, my
wall AC:

If my AC were perfect, this
would be a sine wave. But, this is no sine wave. See how the top of the
waveform is flat? That indicates the presence of harmonics. And this is with
a power strip that we all use in our homes for increasing the number of
sockets. My AC looks like this no matter what I put into the circuit (except
for the PS Audio and ExactPower, which you are about to see). Here is one
with a UPS and several power strips:

Pretty much the same.

OK, now here is what it looks
like, coming through all those power strips and whatnot, but the final item
in the path being the ExactPower EP15:

Whoa! Adios noise, harmonics,
and hello sine wave. The EP15 and PS Audio products are the ONLY ones we
have tested that can do this. The sonic benefits of reduced noise in the
power translate to the same thing in the audio circuits. Less noise. Audio
amplifier power supplies convert AC to DC before sending it to the music.
Those power supplies are not perfect. Any noise in the incoming AC will get
through to the music, even in just tiny amounts. So, the less noise in the
AC supply, the less noise that the amplifier has to deal with. Simple as
that.

One thing that the EP15 does
not do, is supply balanced power. If your incoming AC is unbalanced, which
it is for North American 120 Volts, 60 Hz, the EP15 output is unbalanced
too. Now, we at Secrets believe strongly in the benefits of balanced AC.
Because of common mode rejection, any noise that gets into the AC power
cords after a balanced AC is supplied to the sound system, will be
eliminated. Since power cords are antennae, this is a good thing.

So, how do we balance the
EP15?

There are a number of balanced
transformers out there that you can simply connect to the output of the
EP15. Many are expensive, but there are some that come at reasonable cost.
The BPT (www.b-p-t.com) represents a
best-buy kind of value, and we have used them. They are a no-frills version
of transformers costing much more. So, total cost of the EP15 and a balanced
transformer will be about $2,500. The package will be very efficient, not
get hot, and can fit in reasonable spaces.

The Sound

We have discussed the sonic
benefits of clean AC many times. It is especially evident with mass market
receivers. Less harshness is the most obvious thing. I suspect that is the
result of high frequency noise being reduced. The benefits of eliminating
the AC harmonics will be less hum. The EP15's 15 amp rating let us crank our
entire system, with three Velodyne HGS-18s in the circuit, to full output
with no problems at all. The voltage regulation allows a deeper bass too,
since low frequencies require more power, and a sagging AC wall socket robs
the bass of deep impact. What happens is that the EP15's own power supply
delivers the extra current into the circuit, along with the wall's current,
when the demand is there. Then, the EP15 replenishes its power supply during
the aftermath of all those explosions.

Conclusion

The ExactPower EP15 is a
winner, big time. It gives you the 60 Hz sine waves that you are paying for
but not getting from the power company, keeps it at 120 volts no matter what
your subwoofers are demanding, and all at the price we were paying for fancy
filters in the past. Add a balanced transformer, and you have clean, pure,
balanced power. You can't ask for more. Highly recommended.